JPH0810282B2 - Light transmitting fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plastic optical transmission fiber having a core-sheath double structure and excellent heat resistance.

[Prior Art] Conventionally, as a light transmitting fiber, an inorganic glass optical fiber having an excellent light transmitting property over a wide wavelength range is known. However, glass-based fibers have poor workability, are weak against bending stress, and are expensive, and thus light-transmitting fibers based on synthetic resins have been developed. A light-transmitting fiber made of a synthetic resin has a polymer having a high refractive index and good light transmission as a core component, and a polymer having a lower refractive index than this core component polymer and a transparent polymer is a sheath component. As obtained by producing a fiber having a core-sheath dual structure. An amorphous material is preferable as the core component polymer having high light transmittance, and methyl polymethacrylate or polystyrene is generally used.

Polymethylmethacrylate is not only transparent but also has excellent mechanical properties and weather resistance, and is industrially used as the core material for high-performance plastic optical fibers, and has been developed for applications in the fields of short-range optical communication and optical sensors. Is being promoted. However, since polymethylmethacrylate has a heat distortion temperature of around 100 ° C. and is not sufficiently heat resistant, there are many fields in which application development is restricted, and there is a strong demand for improvement in heat resistance.

As a method of improving the heat resistance of methacrylic resin,
For example, the following method is known.

(1) A method of copolymerizing methyl methacrylate and α-methylstyrene.

(2) A method in which poly-α-methylstyrene is dissolved in a methyl methacrylate monomer and then methyl methacrylate is polymerized (see JP-B-43-1616 and JP-B-49-8718).

(3) A method of copolymerizing methyl methacrylate and N-allyl maleic acid imide (see Japanese Patent Publication No. 43-9753).

(4) A method of copolymerizing methyl methacrylate / α-methylstyrene / maleimide.

(5) A method of polymerizing methyl demethacrylate in the presence of a crosslinked polymer using a polyfunctional monomer (Japanese Patent Laid-Open No. 48-95490).
And JP-A-48-95491).

[Problems to be solved by the invention]

However, in these methods, although the heat resistance of the obtained polymer is improved, the polymerization rate is extremely low, the productivity is remarkably reduced and the polymer is not practical, and the mechanical properties of the obtained polymer are high. Inadequate properties or optical properties,
When it is molded, it is markedly colored or the molding processability is deteriorated, and it has not reached a level where it can be put to practical use.

The object of the present invention is not only to have optical properties, mechanical properties, weather resistance and molding processability comparable to those of polymethacrylic acid ester resins, but also to have excellent heat resistance and productivity. An object of the present invention is to provide a light-transmitting fiber having an excellent light-transmitting property, which is composed of a united body and a sheath component polymer having excellent heat resistance and transparency.

[Means for Solving the Problem] The present invention provides (A) 40 to 98% by weight of methyl methacrylate, (B) 1 to 30% by weight of N-cyclohexylmaleimide and / or N-lower alkylmaleimide and (C). ) 1
To a core component copolymer obtained by copolymerizing a mixture substantially consisting of 30 to 30% by weight of an aromatic vinyl compound, and the core component is coated, and the refractive index of the core component copolymer is 1% or more. It is a light-transmitting fiber made of a sheath component polymer having a low refractive index.

In the light transmitting fiber of the present invention, the methacrylic resin as the core component substantially contains the above-mentioned copolymerization components (A), (B) and (C), and the combination of these components In addition, an unexpected synergistic effect is obtained, and high heat resistance, molding processability, light transmission properties and mechanical properties that are unachievable with conventional copolymer resins are exhibited, and they are also excellent in productivity.
By using the core component copolymer having such characteristics, it is possible to obtain an excellent light transmitting fiber which is well balanced in various performances.

In the light transmitting fiber of the present invention, the core component copolymer is
Substantially (A) 40-98% by weight, preferably 60-93% by weight of methyl methacrylate, (B) 1-30% by weight, preferably 5-20% by weight of N-cyclohexylmaleimide and / or N. -Lower alkyl maleimide and (C) 1 to 30% by weight, preferably 3 to 20% by weight of an aromatic vinyl compound as a copolymerization component. Among the above-mentioned copolymerization components, methyl methacrylate (A) is a component necessary for maintaining the basic optical characteristics, weather resistance and mechanical characteristics of the light transmitting fiber. When the content of the component (A) is less than 40% by weight, the above-mentioned basic properties of the resulting copolymer are insufficiently retained, and when the content of the component (A) is more than 98% by weight, it is obtained. The heat resistance of the resulting copolymer is insufficiently improved.

The specific N-substituted maleimide (B) of the present invention is one of the components that improve the heat resistance of the resulting copolymer, and its content must be 1 to 30% by weight. When this content is less than 1% by weight, the heat resistance of the obtained core component copolymer becomes unsatisfactory, and when it exceeds 30% by weight, the mechanical properties of the obtained copolymer are deteriorated and its productivity is lowered. It becomes unsatisfactory.

Examples of the N-substituted maleimide (B) used in the present invention include N-cyclohexylmaleimide, N-lower alkylmaleimide such as N-methylmaleimide, N-ethylmaleimide, Nn-butylmaleimide, Nt-butylmaleimide and the like. Can be mentioned. Particularly, from the viewpoint of water resistance, N-cyclohexylmaleimide or Nt-butylmaleimide is preferable.

The aromatic vinyl compound (C) is effective in greatly improving the copolymerizability of the component (B), and is also effective in significantly improving the mechanical properties, light transmission performance and molding processability of the resulting copolymer. Have. Such an effect of improving the mechanical performance and the optical transmission performance is unpredictable from the conventionally known copolymerization effect of styrene and the like. The aromatic vinyl compound (C) is used in an amount of 1 to 30% by weight.
If the amount used is less than 1% by weight, the copolymerizability of the resulting mixture will be insufficient, and if it is more than 30% by weight, the optical properties of the resulting copolymer will be unsatisfactory.

Examples of the aromatic vinyl compound (C) used in the present invention include styrene and aralkylstyrenes such as o- and m.
-And p-methylstyrene, 1,3-dimethylstyrene,
2,4-dimethylstyrene, acetylene styrene, p-
Tertiary vinyl styrene, etc., α-methylstyrene, α-ethylstyrene, α-methyl-p-methylstyrene, monovinylidene aromatic hydrocarbons such as vinylnaphthalene, o
Examples thereof include alhalomonovinylden aromatic hydrocarbons such as-, m- and p-chlorostyrene, 2,4-dibromostyrene and 2-methyl-4-chlorostyrene. When the halohalomonovinylidene aromatic hydrocarbon is used for a long period of time, it is necessary to take measures against corrosion of the equipment. From the viewpoint of the balance of productivity and physical properties, it is preferable to use at least one selected from the group consisting of styrene, vinyltoluene and α-methylstyrene. From the viewpoint of improving heat resistance,
In particular, it is preferable to contain α-methylstyrene.

The core component copolymer of the present invention has an intrinsic viscosity of 0.35 to 1.0 dl / g, particularly 0.40, measured in chloroform at 25 ° C.
It is preferably in the range of 0.80 dl / g. Intrinsic viscosity is 0.
If it is less than 35 dl / g, the mechanical properties will be unsatisfactory for practical use, while if the intrinsic viscosity exceeds 1.0 dl / g, molding will be difficult.

The residual monomer amount in the core component copolymer of the present invention is preferably 1.0% by weight or less, and particularly preferably 0.7% by weight or less. If the residual monomer content in the core component copolymer exceeds 1.0% by weight, the heat distortion resistance decreases, and in an extreme case, the foamability due to volatilization during heat processing may impair the transmission property. In particular, the residual N-substituted maleimide (B) in the core component copolymer greatly affects the light-transmitting property, so the residual amount is preferably 0.3% by weight or less, particularly 0.15% by weight or less.

In order to obtain a better synergistic effect of improving the heat resistance by the aromatic vinyl compound (C) and the N-substituted maleimide (B), the number of moles of the N-substituted maleimide (B) in the copolymer is α, and the aromatic When β is the total number of moles of the vinyl compound (C), β / α is preferably adjusted to a range of 0.2 to 5, and particularly 0.5 to 2. If β / α is less than 0.2, there will be many restrictions on manufacturing conditions and productivity will be low. On the other hand, the copolymer having β / α of more than 5 tends to be colored, and the physical properties of the methacrylic resin such as transparency tend to be deteriorated.

The core component copolymer used in the present invention is substantially obtained from the copolymer components (A), (B) and (C), but in addition to these copolymer components, a small amount of It may preferably contain 20% by weight or less of the copolymerization component (D). As the copolymer (D), for example, a monomer having an ethylenic double bond such as methacrylic acid, acrylic acid, methyl acrylate, ethyl acrylate or vinyl acetate is preferable.

The core component copolymer is the above-mentioned copolymer component (A),
The mixture of (B), (C) and, if desired, the component (D) can be produced by a radical polymerization initiator and by a commonly used polymerization method such as bulk polymerization, solution polymerization or suspension polymerization. . The polymerization is carried out by heating to a temperature of 50 to 180 ° C, preferably 65 to 150 ° C.

As the radical polymerization initiator used for preparing the core component copolymer, those used in general radical polymerization, for example, azobisisobutanol diacetate, 1,1-azobiscyclohexanecarbonitrile, azobis Isobutyronitrile, 2,2'-azobis- (2,4-
Azobis-based catalysts such as dimethyl valeronitrile), di-
t-butyl peroxide, dicumyl peroxide,
Examples include diacyl peroxide-based catalysts such as lauroyl peroxide, benzoyl peroxide, and bis (3,5,5-trimethylhexanoyl) peroxide, and percarbonate-based catalysts.

In the light transmitting fiber of the present invention, the core component is covered by the sheath component. The sheath component is formed by a polymer having a refractive index lower than that of the core component copolymer by 1% or more. The polymer preferably has a glass transition point of 80 ° C. or higher and is substantially transparent.

The sheath component polymer is described, for example, in JP-B-43-8978, JP-B-56-8321, JP-B-56-8322, JP-B-56-8323 and JP-A-56-60243. Polymers of fluorinated alcohol esters of methacrylic acid, copolymers of vinylidene fluoride and tetrafluoroethylene as described in JP-B-53-42260, polymethylmethacrylate, polysiloxane and ethylene-acetic acid. A vinyl copolymer or the like is used. The methacrylic acid-fluorinated alcohol ester has the general formula Or (In the formula, X is a hydrogen atom, a fluorine atom or a chlorine atom, and n is 1 to
6 is an integer, m is an integer of 1 to 10, p is an integer of 1 to 10, R ₁ and R ₂ are each a hydrogen atom, a methyl group, an ethyl group or a trifluoromethyl group). To be Such a methacrylic acid fluoroalkyl ester may be polymerized alone, or may be copolymerized with another polymerizable vinyl monomer. Examples of such vinyl monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, dichlorohexyl methacrylate, glycidyl methacrylate, methacrylic acid, acrylic acid, maleic anhydride, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate. , 2-ethylhexyl acrylate, benzyl acrylate, glycidyl methacrylate, glycidyl acrylate, styrene,
α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, -chlorostyrene, 2,4-dichlorostyrene, p-methoxystyrene, acrylonitrile, methacrylonitrile, vinyl acetate, methyl vinyl ketone, hydroxypropyl acrylate, hydroxyethyl Examples include acrylate. Two or more of these monomers may be combined and copolymerized. Methyl methacrylate is particularly preferred from the viewpoint of providing a transparent copolymer.

The sheath component polymer can be produced by radically polymerizing the polymer component by a conventional method. As the polymerization catalyst, a usual radical polymerization initiator, for example, di-t-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, lauroyl peroxide, 2,5-dimethyl-2,5-
Organic peroxides such as t-butylperoxyhexane, t-butylperoctanoate, t-butylperisobutyrate, and t-butylperoxyisopropylcarbonate, and methyl-2,2'-azobisisobutyrate, 1,1′-azobiscyclohexanecarbonitrile, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, 2
-Albamoyl-azobisisobutyronitrile, 2,2 '
Examples thereof include azo compounds such as -azobis-2,4-dimethylbereronitrile and 2,2'-azobisisobutyronitrile.

Examples of the polymerization method include emulsion polymerization, suspension polymerization, bulk polymerization and solution polymerization, and the bulk polymerization method is preferable in order to obtain a high-purity polymer.

In the light transmitting fiber of the present invention, the value of the refractive index of the sheath component needs to be lower than that of the core component by 1% or more. When the difference in refractive index between the two components is less than 1%, the numerical aperture of the resulting light-transmitting fiber becomes too small, making it practically difficult to use. Also, if the refractive index of the sheath component is greater than that of the core component, the resulting fiber will not transmit light.

Since the light transmitting fiber may be exposed to a high temperature for a long time, it is preferable that it has good durability under such conditions. For this purpose, the sheath component polymer is 70 ° C or higher, especially
It preferably has a heat distortion temperature of 90 ° C. or higher and a glass transition temperature of 80 ° C. or higher.

The core-sheath dual structure light transmitting fiber of the present invention is manufactured by the following method.

(1) A composite spinning method in which a core component copolymer and a sheath component polymer are each melted and extruded into a special nozzle core-sheath structure.

(2) A coating method of forming a core component fiber from the core component copolymer, coating the core component fiber with the solution of the sheath component polymer, and then removing the solvent from the coating layer. When forming the fibers of the core component, the core component copolymer may be continuously bulk polymerized by the method described in JP-B-48-131391, and then the core component copolymer may be spun to form the core component fiber. This method is effective in reducing the loss of optical transmission performance of the core component.

〔The invention's effect〕

The light-transmitting fiber of the present invention is remarkably superior in heat resistance and durability as compared with the conventional plastic light-transmitting fiber containing polymethylmethacrylate or polystyrene as a core component. Further, the optical transmission fiber of the present invention is far superior in optical transmission performance to the conventional optical transmission fiber having polycarbonate as a core component (its optical transmission distance is only a few meters).

Further, the light transmitting fiber of the present invention is relatively inexpensive, has good handleability, and is extremely well balanced in various characteristics. Therefore, the optical transmission fiber of the present invention can be used, for example, for wiring in the engine room of an automobile, and has extremely high industrial significance and value as it can respond to the progress of car electronics.

In the following examples, the optical transmission performance of the fiber is shown in
The measurement and evaluation were carried out by the device shown in FIG. The measurement conditions are as follows.

Interference filter (main wavelength) 650 μm Total fiber length 5 m Fiber cut length 4 m Bobbin diameter 190 mm Example 1 Methyl methacrylate 8000 g, N-cyclohexylmaleimide 1180 g, α-methylstyrene 500 g, styrene 320
A monomer mixture consisting of 30 g of azobisisobutyronitrile and 16 g of n-octyl mercaptan was prepared. Aerosol OT (manufactured by Ciba-Geigy) was added to this mixture as a release agent so as to have a concentration of 50 ppm, dissolved, and then a cell formed by two tempered glass plates facing each other at intervals of 6 mm through a polyvinyl chloride gasket. A thermocouple was set in the cell, the composition was injected into the cell, and the cell was immersed in warm water at 78 ° C. for polymerization and curing. Measure the time (curing time) from the immersion in warm water to the peak internal temperature (curing time), and 30 minutes after the peak temperature is reached, remove from the warm water and then in an air furnace at 120 ° C for 2 hours. Heat treated. After cooling, the cell was removed, and the obtained resin plate having a plate thickness of about 6 mm was crushed in a clean box to obtain a core component copolymer.
Melt index (MI) of the obtained core component copolymer
(230 ° C load 3.8 kg) was 2.2, refractive index (η _D ) was 1.50, and heat distortion temperature was 120 ° C.

Separately, 50 parts by weight of 2,2,2-trifluoroethyl methacrylate, 50 parts by weight of methyl methacrylate and 0.3 parts by weight of n-octyl mercaptan were mixed and dissolved, and then 0.025 parts by weight of a polymerization catalyst azobisbutyronitrile was added and dissolved. The above mixture was poured into a cell formed of two tempered glass plates facing each other at intervals of 5 mm through a polyvinyl chloride gasket, and the mixture was immersed in warm water at 70 ° C. to polymerize and cure. Thirty minutes after the peak temperature was reached due to the heat of polymerization, the cell was taken out of warm water and then heat treated in an air oven at 130 ° C. for 2 hours. After cooling, remove the cell, crush the resin solution obtained in a green box, and set the MI value (230 ° C load).
3.8 kg) 5.0, an intrinsic viscosity of 0.52 dl / g, a refractive index of 1.445 and a heat distortion temperature of 98 ° C were obtained as a sheath component polymer.

The obtained core and sheath both component copolymers were fed to a vent-type composite spinning machine having a core-sheath two-layer structure spinneret, taken at a spinning temperature of 250 ° C., a spinning speed of 3 m / min, and further continuously. It was stretched 2.0 times at 170 ° C. and wound up.

The obtained fiber has a core component diameter of 980 μm and a sheath component thickness of 10 μ.
m, the weight ratio of the core component to the sheath component was 96: 4, and the fiber had a concentric circular structure. The optical transmission loss of this optical transmission fiber was 900 dB / kn, and the optical signal could be sufficiently transmitted at a length of 10 m.

The obtained light-transmitting fiber was used as a first jacket with a crosshead type cable processing machine, and carbon black polyethylene was coated so that the outer diameter was 1.6 mm.
As a jacket, a polyester elastomer containing carbon black was coated to an outer diameter of 2.2 mm, and an optical cable with an optical transmission loss of 920 dB / kn was obtained.

Cut out 10 m of this optical cable and use one end face as a light source (6
Fixed to 50mm interference filter), the other end was connected and fixed to a photodiode, the middle part of the optical cable was exposed to a hot air heating furnace at 120 ° C, the change in the amount of transmitted light was traced, and the heat resistance durability of the optical cable was evaluated. did.

As a result, this optical cable showed a stable decrease in the amount of transmitted light of 20% even after 1000 hours, showing very little change and stable heat resistance and durability.

Comparative Examples 1 to 4 The optical compositions of Comparative Examples 1 to 4 were obtained in the same manner as in Example 1 except that the composition of methyl methacrylate was as shown in Table 1 for comparison. Table 2 shows the results of comparative evaluation of the optical transmission performance and heat resistance durability of this optical cable with those of Example 1.

As is clear from these results, the optical transmission fiber of the present invention had a low light amount loss that was sufficient for communication of an optical signal of 10 m in length, and was also extremely excellent in heat resistance and durability. On the other hand, Comparative Examples 1 to 4 showed defects such as extremely large optical transmission loss (Comparative Example 2) and unsatisfactory heat resistance and durability (Comparative Examples 1, 3 and 4).

Example 2, Comparative Examples 5 and 6 The monomer mixture was as shown in Table 3 and the other conditions were the same as in Example 1, and the results shown in Table 4 were obtained. In the table
GAT is azobisisobutyronitrile, and M is n-octyl mercaptan.

The optical transmission fibers of Comparative Examples 5 and 6 were inferior in optical characteristics and had extremely low mechanical characteristics, and thus were practically difficult to use.

Example 3 In a flask having an internal volume of 5000 ml, 2700 g of deionized water, 0.3 g of a copolymer of sodium salt of methyl methacrylate 2-sulfoethyl methacrylate and 9 g of a dispersant component of 9 g of sodium sulfate were charged, and then 80 parts of methyl methacrylate, N-cyclohexylmaleimide 12 parts, α-methylstyrene 8
Part, n-octyl mercaptan 0.15 part and azobisisobutyronitril 0.35 part, 1800 g of a monomer mixture was charged, and the mixture was stirred at 400 rpm while substantially removing oxygen.
Suspension polymerization was carried out by heating at 80 ° C for 3 hours. The polymerization system is stable until the end of the polymerization, and almost no polymer particles attached to the walls of the flask and the stirring blades or polymer beads floating above the water surface are observed, and polymer beads with an average particle size of 0.28 mm are obtained. Was given. After washing, dehydration and drying, polymer beads are rewashed with a large amount of distilled and purified methanol to remove residual monomers and dried, heat distortion temperature 122 ° C, intrinsic viscosity 0.50dl / g, MI2.5, refraction Rate 1.50
A core component copolymer was obtained.

2,2,2-trifluoroethyl methacrylate / methyl methacrylate / methacrylic acid (15/8
(0/5 weight ratio) Copolymer (refractive index 1.48, heat distortion temperature 105 ℃)
Was used, and an optical fiber cable was obtained in the same manner as in Example 1. The characteristics of the optical cable are shown in Table 5.

Example 4 An optical cable was obtained in the same manner as in Example 3, except that the composition of the monomer mixture was as follows. The characteristic is the fifth
Shown in the table.

Methyl methacrylate 80 parts N-methylmaleimide 10 parts p-Methylstyrene 10 parts Azobisisobutyronitrile 0.3 parts n-octyl mercaptan 0.15 parts Example 5 Using a system in which a storage tank, a continuous supply pump and a first reaction tank equipped with a paddle spiral stirrer, a plug flow type second reactor, a reactant extraction pump, and a volatiles separator are connected together, A polymer was produced. The inner volume of the first reaction tank was 40 liters, the inner volume of the second reactor was 20 liters, and a twin-screw SCREVENT extruder was used as the volatile matter separation device.

The raw material monomer mixture is a filter made of polytetrafluoroethylene with a thickness of 0.1 μm (Fluoropore EPOI).
O) made by Sumitomo Electric Co., Ltd.) to remove impurities. The composition of the raw material monomer mixture was 80 parts by weight of methacrylic methyl, 4 parts of α-methylstyrene, 5 parts of styrene,
11 parts of N-cyclohexylmaleimide, 0.13 parts of n-octyl mercaptan, 0.30 parts of azobisisobutyronitrile and 33 parts of methyl ethyl ketone. Under a nitrogen atmosphere, this mixture was fed into a first reaction tank whose internal pressure was 2 kg / cm gauge pressure and temperature was 85 ° C using a feed pump, and a thickness of 0.1 μm.
m polytetrafluoroethylene filters (Fluoropore EPOIO manufactured by Sumitomo Electric Industries, Ltd.) of m were piled up and passed over, and the mixture thus continuously supplied was polymerized while being sufficiently stirred in the reaction tank. The average residence time of the mixture in the first reaction tank was 4.0 hours, and the average polymerization rate was 48%.
The reaction mixture was fed into the second reactor and continuously heated from 80 ° C to 150 ° C. The polymerization rate at the outlet of the second reactor was 90%.

The temperature of the vent extruder, which also functions as a volatile matter separator, was 250 ° C. at the vent portion, 245 ° C. at the extrusion portion, and the degree of vacuum at the vent portion was 5 mmHg. The core component copolymer discharged from the vent extruder was introduced into the spinning head directly connected thereto. Separately, the sheath component polymer was introduced into the spinning head from another extruder installed in parallel with the vent extruder, where the core component copolymer and the sheath component polymer were formed into a core-sheath structure. Composite spinning at 245 ° C.

The sheath component polymer was the same as in Example 3. The residual amount of the monomer in the core component copolymer was 0.1% by weight or less, and the refractive index was 1.50. The weight ratio of the core component to the sheath component in the obtained heart-sheath structure fiber is 90:10,
Its outer diameter was 1 mm. The optical transmission of the fiber thus obtained was 960 dB / km at a wavelength of 650 μm, which was extremely excellent. The cable made of this composite fiber showed an extremely excellent heat resistance and durability because the reduction rate of the amount of transmitted light after heat treatment at 120 ° C for 1000 hours was only 15%.

Claims (5)

[Claims] 1. A) 40 to 98% by weight of methyl methacrylate, (B) 1 to 30% by weight of N-cyclohexylmaleimide and / or N-lower alkylmaleimide and (C) 1.
To a core component copolymer obtained by copolymerizing a mixture substantially consisting of 30 to 30% by weight of an aromatic vinyl compound, and the core component is coated, and the refractive index of the core component copolymer is 1% or more. A light transmitting fiber made of a sheath component polymer having a low refractive index. 2. The light transmitting fiber according to claim 1, wherein the sheath component polymer is a transparent polymer having a glass transition point of 80 ° C. or higher. 3. The light transmitting property according to claim 1, wherein the aromatic vinyl compound is at least one selected from the group consisting of styrene, vinyltoluene and α-methylstyrene. fiber. 4. When α is the number of moles of N-cyclohexylmaleimide and / or N-lower alkylmaleimide and β is the number of moles of the aromatic vinyl compound, β / α is in the range of 0.2 to 5. The optical transmission fiber according to claim 1, wherein 5. The sheath component polymer is at least one selected from the group consisting of a polymer of a fluorinated alcohol ester of methacrylic acid, a vinylidene fluoride-tetrafluoroethylene copolymer, and polymethyl methacrylate. The light transmitting fiber according to claim 1.